Many people will be somewhat surprised that the American Dialect Society's "Word of the Year" choice was because in its use with a noun phrase (NP) complement (though the Megan Garber's Atlantic Monthly article on it nearly two months ago should perhaps have been a tip-off). It seems to be unprecedented for a word in a minor category like preposition to be chosen rather than some emergent or fashionable word in one of the major lexical categories: recent winners have included 2012's hashtag (noun), 2011's occupy (verb), 2010's app (noun), 2009's tweet (noun and verb), 2008's bailout (noun), 2007's subprime (adjective), 2006's plutoed (past participle of verb meaning "downgrade in status"), and 2005's truthiness (noun). And it also seems to be unique in representing a new syntactically defined word use within a given category rather than a new (or newly trending) word. The syntax of because calls for a little discussion, I think, given that Megan Garber thinks the word has become a preposition for the first time, and every dictionary on the market is wrong in the part-of-speech information it gives about the word (write to me if you can find a dictionary of which this is not true: I'd love to see one).

What the American Heritage Dictionary (AHD) says about because will do as a basis for discussion, since the dictionaries pretty much all agree (they basically just plagiarize each other). There are some that say because is an adverb (Wiktionary does, for example), which is stupid in various ways I won't go into here, but what the AHD reports is more standard (it agrees completely with Webster's Third New International Dictionary): it says that because is a "conjunction", but there is also a word spelled because of, which is a preposition. Both claims are flamingly and demonstrably wrong.

Traditional grammar recognizes two types of "conjunction" (I put the word in scare quotes because, although famililar, it is a most undesirable choice of terminology, since it has a different use in logic): there are "subordinating conjunctions" and "coordinating conjunctions". Because doesn't resemble the archetypal members of either class of words.

Why because isn't a "conjunction"

First, let's consider the "subordinating conjunctions" (The Cambridge Grammar calls them subordinators). The archetypal exemplar is the unstressed word that (not the stressed demonstrative with the same spelling). It introduces subordinate clauses, as in Ted says that the world is flat, which are nearly always complements (i.e., they are required or specifically licensed by the foregoing main clause word, in this case believe). That is meaningless in its own right, and often omissible (Ted says the world is flat is grammatical and has the same meaning). Preposing the constituent that it introduces (i.e., shifting that and the following clause to the beginning of the main clause) generally sounds pretty weird: the strikingly odd sentence ??That the world is flat, Ted says would need a special context where different things Ted says are being contrasted with one another. It is not at all just a variant of Ted says that the world is flat.

None of this holds for because, as used in sentences like Ted is ridiculed because he holds ridiculous beliefs. Because introduces constituents that are hardly ever complements. In The reason he left is because he was not respected the because phrase is the complement of is, and in the colloquial Just because he's a Republican doesn't mean he's evil the subject is the phrase beginning just because. But mostly because phrases are adjuncts. Thus *Ted says because the world is flat is not grammatical at all due to the lack of a complement for say (you would have to understand it elliptically, with something missing after the verb says, so it means "Ted says it is because the world is flat"). And of course because is not meaningless: it contributes a crucial logical relation of cause or reason. It can therefore never be omitted without radical change to the meaning and usually the grammatical permissibility of the sentence (*Ted is ridiculed he holds ridiculous beliefs is not grammatical). Moreover, shifting the whole because-phrase to the front is perfectly normal: Because he holds ridiculous beliefs, Ted is ridiculed is perfectly normal in lots of contexts. In short, because is nothing like that in its syntax or its semantics.

What about the other "conjunctions"? The classic "coordinating conjunction" (which CGEL calls a coordinator) is and, which introduces non-initial components of coordinate constituents, as in Roses are red and violets are blue. Switching the positions of the two clauses separated by the and normally gives a grammatical result with the same truth conditions: Violets are blue and roses are red is true if and only if Roses are red and violets are blue is true. Preposing the and plus what follows it is never permitted: *And violets are blue, roses are red is totally ungrammatical.

The opposite of all of this holds for because. The sentence Roses are red because violets are blue has a completely different meaning from Violets are blue because roses are red (the direction of the causal arrow is reversed). And Because violets are blue, roses are red is a grammatical alternative way of expressing the same thing as Roses are red because violets are blue.

So why do all dictionaries make the self-evidently false claim that because is a "conjunction" and thus either like that or like and? In short, because they are all lazy followers of a stupid tradition that has needed rethinking for 200 years (some would say it's more like 2,000 years, because it originates in classical times). They are locked into system of respecting an ancient analysis that doesn't work.

The "conjunction" notion is based on the extremely vague notion of joining: a "conjunction" is supposed to be a word that "joins" two elements together. Very little thought is required to see that if using C to "join" A together with B means simply forming the sequence "A C B" then almost anything can be called a "conjunction"; and no stricter and more tightly framed definition has been given. (It couldn't be, given the diversity of what it would have to cover: subordination of finite and nonfinite complement and adjunct clauses, coordination of clauses, and coordination of other things such as NPs.)

Why because of isn't a preposition

That brings us to the similarly brainless claim that there is a preposition spelled because of. I'm not going to say that the dictionary should never recognize something as a word if it has a space in it; foreign-derived proper nouns like Santa Cruz are best thought of as words rather than phrases, and there may be some space-containing words other than proper nouns (sort of is probably an example). But because of isn't one of them.

I don't need elaborate arguments to convince you of this. I simply searched the Wall Street Journal corpus (44 million words from the late 1980s that has served as a convenient testbed for all sorts of computational linguistic experiments over the past twenty years), looking for cases of because and of with some stuff in between. Within half a second my laptop provided these results:

If among the intellectual beliefs of Latin America the idea of democracy itself is so denigrated, it is because, in great part, of our public universities.

Higher-priced goods were the best sellers in lines ranging from toys to apparel, partly because, some retailers thought, of the new tax law, which will eliminate deductions for sales taxes beginning next year.

Chavez was more restrained this time because, he later revealed, of a rib injury suffered sparring at promoter Don King's famous, $1,000-a-day Cleveland training lair six weeks ago.

"I want to avoid saying Europe is a role model for North America," says Robert C. Stempel, who won the president's job at GM last May because, it is widely believed, of the company's improvement overseas.

These don't just have words and spaces in between because and of; they actually have commas in there! Do you want to posit words in the dictionary that have commas and spaces and sequences of three or four words inside them? Do you want to propose that the dictionary should include not just the one word because of but several million others like because, some retailers thought, of and because, it is widely believed, of? If you do, you're a fruitcake, and I'm not addressing you. If you are a Language Log reader you will see what I mean. There is no preposition because of; these are two separate words, with their own functions, capable of being widely separated by other words.

The correct part-of-speech classification

Of, naturally, is a preposition. It is the commonest and most stereotypical of all prepositions in English. It heads preposition phrases (PPs) like of our public universities. So what should we say about because? Contrary to all the dictionaries, it is a preposition. As its complement (the phrase that follows it to complete the PP) it may take either a clause (as in the PP because he holds ridiculous beliefs) or a PP with of as its head (as in the PP because of our public universities). Some prepositions can occur with no complement (as in We went in), some require an NP (as of does) some require a clause (as although does), and some require a PP (like out in those uses that do not involve exiting from delimited regions of space: notice that They did it out of ignorance is grammatical but *They did it out ignorance is not).

The change that has caught the eye of the American Dialect Society is simply that because has picked up the extra privilege already possessed by prepositions like of: it now allows a noun phrase (NP) as complement (with a subtly different shade of meaning: because money seems to express only a rather vague and non-serious commitment to the idea that the reason is financial). So syntactically speaking, in the following table of prepositions (in red) and their complement categories (in blue), a single entry has been changed (✓ means "grammatically permitted", * means "grammatically forbidden", and % means "grammatically permitted in some semantically limited contexts"):

(none)

NP

of-PP

Clause

in

✓

✓

*

*

out

✓

%

%

*

since

✓

✓

*

✓

of

*

✓

*

*

because

*

*

✓

✓

The language has simply added to its stock of grammatical possibilities (as it can, because syntax) a single check mark, replacing the green asterisk in the last row. Think of it as the first American Dialect Society grammatical Check Mark of the Year. And if you would like the dictionary to cover (as Wiktionary does) the colloquial use of because on its own as an imperious but uninformative answer to a why-question ("Why do I have to wear my mittens, mommy?" "Because!"), then we can get rid of the first asterisk in the last row as well, and the relevant line will look like this:

(none)

NP

of-PP

Clause

because

✓

✓

✓

✓

That represents because as a preposition that is sometimes used with no complement, and sometimes (in the new usage that the ADS has just recognized) with an NP complement, and also (much more commonly) with an of-PP complement or a bare finite clause complement. It's a syntactically accurate classification, which dictionaries ought to adopt—but don't hold your breath waiting for them.

[This post was revised on Monday 6 January 2014 and again on 16 July 2014; several small errors were corrected and a few additional points were added. For a more thorough treatment of the topic of classifying words like because, see my paper "Lexical categorization in English dictionaries and traditional grammars", in Zeitschrift für Anglistik und Amerikanistik57 (3), 255–273 (2009); uncorrected final proof PDF here. —GKP]